CN116679329A - Beidou space-time reference accurate characterization method and system based on state domain space - Google Patents

Abstract

A Beidou space-time reference accurate characterization method and system based on a state domain space belong to the technical field of satellite navigation, and comprise the following steps: obtaining the position of a satellite through satellite orbit correction information; obtaining a satellite clock through satellite clock correction; obtaining pseudo-range and phase observations that do not include individual time-dependent biases through satellite bias correction; obtaining inclined total electronic content information through the vertical total electronic content information, and further obtaining pseudo-range and phase observation without ionosphere deviation; and obtaining the user ranging accuracy through a table by using the user ranging accuracy index. According to the invention, through establishing the Beidou space-time reference based on SSR, the technical problem of non-differential and non-combined Beidou navigation and positioning is solved, PPP-RTK is finally realized, and the method has the expandable advantage in the aspects of supporting infinite user quantity, different types of applications and supporting various modern GNSS, frequencies and signals.

Description

Method and system for accurate characterization of Beidou space-time reference based on state domain space

technical field

The invention relates to the technical field of satellite navigation and positioning, in particular to a method and system for accurately representing Beidou time-space references based on state domain space.

Background technique

The need for a standardized State Space Representation (SSR) Global Navigation Satellite System (GNSS) correction data format was agreed many years ago when the International GNSS Service (IGS) developed and analyzed the Precision Point Positioning (PPP) technology, industry The world proposes to use PPP-RTK technology. RTCM Special Committee SC-104 formed a working group in 2007. SSR technology is widely regarded as an advanced and flexible GNSS correction method because of its scalability advantages in supporting an unlimited number of users, different types of applications, and supporting various modern GNSS, frequencies, and signals.

The RTCM-SSR working group defined the SSR concept and real-time reliability messages for all precision classes, including ambiguity resolution (RTK quality). Its proposed timeline/work plan includes the following major steps: Phase 1, satellite orbit, satellite clock, and satellite code bias information to enable dual-frequency receivers for pseudorange-based real-time (RT)-PPP; phase 2, vertical total electronic Content (VTEC) ionospheric information, enabling pseudorange-based RT-PPP for single-frequency receivers; satellite phase bias information, enabling phase-based RT-PPP; Phase 3, ionospheric tilted total electron content (STEC) and tropospheric information , to achieve PPP-RTK; stage 4, compression to reduce bandwidth.

Standardized RTCM-SSR information for GPS and GLONASS was first published on July 1, 2011, in Amendments 1-5 of "RTCMSTANDARD 10403.1". So far only RTCM Phase 1 information has been standardized, and only that covering GPS and GLONASS. Subsequently, IGS developed and published an open format standard including Phase 1 and Phase 2 messages for multi-GNSS SSR corrections. In particular, it supports the real-time services of the IGS and wider research and scientific applications. Although a different message format is used, the basic content of IGS-SSR is compatible with that of RTCM-SSR.

The existing Beidou navigation system lacks a space-time benchmark representation method based on the state domain. The original space-time reference representation method based on the observation domain cannot achieve non-difference and non-combined navigation and positioning. The number of users and other aspects are subject to many restrictions. The present invention aims to support the realization of non-difference and non-combined Beidou navigation and positioning by establishing an accurate characterization method of Beidou space-time reference based on state domain space.

Contents of the invention

In order to overcome the problems existing in the prior art, the object of the present invention is to provide a method and system for accurately characterization of the Beidou space-time reference based on the state domain space. According to the source of Beidou's observation errors, the method establishes observation equations, independently solves each observation error, and forms a real-time absolute positioning (PPP-RTK) method that does not rely on the observation of the main station and has an accuracy comparable to that of real-time relative positioning (RTK).

The present invention is realized by following technical scheme:

The present invention provides an accurate characterization method of the Beidou space-time reference based on the state domain space, comprising the following steps:

Step 1, obtain the position of the satellite through the SSR satellite orbit correction information;

Step 2, correcting the SSR satellite clock to obtain the satellite clock;

Step 3, through SSR satellite bias correction, obtain pseudorange and phase observations that do not contain individual time-dependent bias;

Step 4, through the vertical total electron content (VTEC) information of the SSR, the oblique total electron content (STEC) information is obtained, and then the pseudorange and phase observations without ionospheric bias are obtained;

Step 5, according to the SSR user ranging accuracy (URA) index, the user ranging accuracy is obtained through the table.

Further, in step 1, the SSR satellite orbit correction information uses a satellite fixed coordinate system, which includes orbit correction parameters in three directions: radial, tangential and normal.

Further, in step 2, the SSR satellite orbit correction is the correction of the satellite orbit calculated based on the satellite broadcast parameters of the GNSS-ICD algorithm, and the SSR satellite clock correction is also calculated according to the specific GNSS satellite broadcast parameters of the GNSS-ICD algorithm. inferred.

Further, in step 3, pseudoranges that do not contain individual time-dependent biases and phase /> Observations are obtained from pseudorange and phase raw observations through the following mathematical expression:

,

,

in, and /> SSR bias correction corresponding to pseudorange and phase respectively, /> and /> are pseudorange and phase raw observations, respectively.

Further, in step 5, the SSR user ranging accuracy index is obtained through the SSR URA message of each satellite, and converted into the user ranging accuracy through the corresponding relationship between the index and the value.

The present invention also relates to a Beidou space-time reference accurate characterization system based on state domain space, including:

The satellite position acquisition module is used to correct the information through the SSR satellite orbit to obtain the position of the satellite;

The satellite clock acquisition module is used for correcting the SSR satellite clock to obtain the satellite clock;

The pseudorange and phase observation module is used to obtain pseudorange and phase observations that do not contain individual time-dependent biases through SSR satellite bias correction;

The pseudorange and phase observation module without ionospheric bias is used to obtain the tilted total electron content (STEC) information through the SSR vertical total electron content (VTEC) information, and then obtain the pseudorange and phase observation without ionospheric bias;

The user ranging accuracy module is configured to use the SSR user ranging accuracy (URA) index to obtain the user ranging accuracy through a table.

The present invention also relates to an electronic device comprising:

at least one processor; and,

a memory communicatively coupled to the at least one processor; wherein,

The memory stores instructions executable by the at least one processor, the instructions are executed by the at least one processor to enable the at least one processor to perform the method.

The present invention also relates to a non-transitory computer-readable storage medium storing computer instructions for causing the computer to execute the method.

The technical solution of the present invention can realize the following beneficial technical effects:

The present invention solves the problem of non-difference and non-combined Beidou navigation and positioning technology by establishing the SSR-based Beidou space-time reference, and finally realizes PPP-RTK, which supports unlimited users, different types of applications, and various modern GNSS, frequency and The signaling aspect has the advantage of being scalable.

Description of drawings

Fig. 1 is a schematic flow diagram of the Beidou space-time reference accurate characterization method based on the state domain space of the present invention;

Fig. 2 is a flow chart of the accurate characterization method of the Beidou space-time reference based on the state domain space of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are exemplary only, and are not intended to limit the scope of the present invention. Also, in the following description, descriptions of well-known structures and techniques are omitted to avoid unnecessarily obscuring the concept of the present invention.

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

The present invention provides an accurate characterization method of the Beidou space-time reference based on the state domain space, comprising the following steps:

Step 1. Obtain the position of the satellite through the SSR satellite orbit correction information.

The SSR satellite orbit correction information uses a satellite fixed coordinate system, which includes orbit correction parameters in three directions: radial, tangential and normal.

Orbit and clock messages are combined with corresponding values obtained from satellite broadcast messages. The types of broadcast navigation messages used by Beidou navigation satellites are shown in Table 1.

Table 1 Beidou broadcast message types

,

Specifically, the SSR satellite orbit correction information includes orbit correction parameters , orbit correction parameters /> Vectors include three directions: radial, along and cross. Satellite position correction parameters /> Correct parameters by orbit /> The conversion is available as follows:

,

,

,

,

in, That is, the satellite position of the broadcast ephemeris, /> for /> The speed of is the satellite speed of the broadcast ephemeris, /> , /> , /> Unit vectors representing the radial, tangential, and normal directions, respectively.

By further satellite position with broadcast ephemeris Combined to calculate the position of the satellite /> , its calculation formula is as follows:

,

Step 2. Correct the SSR satellite clock to obtain the satellite clock.

The SSR orbit correction is a correction to the satellite orbit calculated based on the satellite broadcast parameters of the GNSS-ICD algorithm. SSR satellite clock corrections are also computed accordingly from specific GNSS satellite broadcast parameters according to the GNSS-ICD algorithm. SSR corrections are not corrections defined per se for any particular GNSS broadcast correction.

SSR clock corrections include parameters for clock corrections corresponding to broadcast satellite clocks , the following expression describes the clock difference in a certain period of time:

,

in, Polynomial coefficients for SSR satellite clock correction information, /> for the current time, /> Acquisition time for SSR satellite clock correction information, /> High frequency correction information for SSR satellite clocks.

Combined with the broadcast satellite clock, the satellite clock is obtained as follows:

,

in, is the satellite time calculated based on the satellite broadcast parameters of the GNSS-ICD algorithm, /> Correction information for SSR satellite clock.

Step 3. Obtain pseudorange and phase observations that do not contain individual time-dependent biases through SSR satellite bias correction.

Each signal transmitted by a GNSS satellite produces an individual time-dependent bias expressed as a function of hardware and software delays. In the GNSS pseudorange (PR) and phase (PHR) (carrier phase) observation equations, there is a linear dependence between individual satellite signal biases and satellite clock errors. Therefore, it is impossible to completely separate all bias and clock parameters during estimation. One of the solutions to overcome this problem is to define a "satellite bias reference", which sets the bias of a certain signal or a linear combination of signals to zero. For example, GPS broadcast clock corrections are based on the fact that the ionosphere-free combination of the P1 and P2 signals (RINEX observation codes C1P and C2P) is unbiased. A similar convention is followed for IGS satellite clock products, applying a bias reference will convert any remaining bias into relative deviations from the bias reference.

In order to avoid using the bias reference convention in the definition of the SSR standard, the absolute signal bias is included in the SSR satellite bias correction information. Each supported signal part needs to transmit a bias parameter. This adds an additional parameter to the number of bits required, but provides maximum flexibility for service providers to choose supported signal and bias reference definitions. The pseudorange and phase bias messages contain absolute values, but can also support the use of DCBs by setting one of the biases to zero.

Pseudoranges that do not contain individual time-dependent biases and phase /> Observations are obtained from pseudorange and phase raw observations through the following mathematical expression:

,

,

in, and /> SSR bias correction corresponding to pseudorange and phase respectively, /> and /> is the original observation.

Step 4. Obtain the tilted total electron content (STEC) information through the vertical total electron content (VTEC) information of the SSR, and then obtain the pseudorange and phase observations that do not include ionospheric bias.

The ionospheric vertical TEC (VTEC) is expressed by spherical harmonics. Spherical harmonics ensure global and continuous ionospheric models and can also be applied to regional representations. It is the first component of the multilevel ionospheric correction.

A high-resolution grid model is used to realize the VTEC representation at the region/continental block level.

,

in, and /> represent the maximum order and order of spherical harmonics, respectively, /> and /> for the current rank and level, /> and /> represent the coefficients of cosine and sine, respectively, /> is the ionospheric puncture point offset, /> is the longitude of the ionospheric puncture point, /> is the latitude of the ionospheric puncture point, /> is a Lagrangian function. further pass the altitude angle of the satellite at the receiver's spherical position /> , and the central angle of the sphere /> , the STEC of this layer can be obtained.

,

Therefore, the impact of the ionosphere on pseudorange and phase observations and /> It can be expressed as:

,

,

Step 5. According to the user ranging accuracy (URA) index of the SSR, the user ranging accuracy is obtained through a table.

Each state parameter is not independent. For example, clock and radial orbit state parameters are related. SSR User Ranging Accuracy (URA), that is, the minimum standard deviation of User Ranging Error (URE) caused by constraining satellite clock error and ephemeris error in the no-fault state, belongs to the unbiased Gaussian distribution. It is used as a single statistical index to describe the quality of all non-dispersive state parameters. The SSR user ranging accuracy index is obtained through the SSR URA message of each satellite, and converted into the user ranging accuracy through the corresponding relationship between the index and the value. The corresponding relationship between SSR URA indicators and user ranging accuracy is shown in the following table.

Table 2 Correspondence between SSR URA index and user ranging accuracy

,

In summary, the independence of the error source is completed through steps 1-4, the observation model is established, and then the observation model is solved to complete the positioning; the quality of the non-dispersive parameters is evaluated through step 5.

Aiming at the Beidou navigation system, the present invention provides an accurate characterization method of the Beidou space-time reference based on the state domain space in combination with the international advanced state domain space standard. Fill in the gap in the expression method of the self-developed satellite navigation system SSR in China, and provide correction information basis for various positioning modes (single-frequency/multi-frequency, pseudo-range/phase RT-PPP and PPP-RTK) of Beidou-related real-time services standard.

The present invention also relates to a Beidou space-time reference accurate characterization system based on state domain space, including:

The satellite position acquisition module is used to correct the information through the SSR satellite orbit to obtain the position of the satellite;

The satellite clock acquisition module is used for correcting the SSR satellite clock to obtain the satellite clock;

The pseudorange and phase observation module is used to obtain pseudorange and phase observations that do not contain individual time-dependent biases through SSR satellite bias correction;

The pseudorange and phase observation module without ionospheric bias is used to obtain the tilted total electron content (STEC) information through the SSR vertical total electron content (VTEC) information, and then obtain the pseudorange and phase observation without ionospheric bias;

The user ranging accuracy module is configured to use the SSR user ranging accuracy (URA) index to obtain the user ranging accuracy through a table.

The present invention also relates to an electronic device comprising:

at least one processor; and,

a memory communicatively coupled to the at least one processor; wherein,

The memory stores instructions executable by the at least one processor, the instructions are executed by the at least one processor to enable the at least one processor to perform the method.

The present invention also relates to a non-transitory computer-readable storage medium storing computer instructions for causing the computer to execute the method.

To sum up, the present invention provides a method and system for accurate characterization of the BeiDou space-time reference based on the state domain space, including the following steps: obtaining the position of the satellite by correcting the information of the SSR satellite orbit; obtaining the position of the satellite by correcting the SSR satellite clock Clock; through SSR satellite bias correction, obtain pseudo-range and phase observations that do not contain individual time-dependent bias; through SSR vertical total electron content (VTEC) information, obtain tilted total electron content (STEC) information, and then obtain ionospheric The pseudo-range and phase observation of the deviation; through the SSR user ranging accuracy (URA) index, the user ranging accuracy is obtained through the table. The present invention solves the problem of non-difference and non-combined Beidou navigation and positioning technology by establishing the SSR-based Beidou space-time reference, and finally realizes PPP-RTK, which supports unlimited users, different types of applications, and supports various modern GNSS, frequencies and signals. It has the advantage of being scalable.

It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principle of the present invention, and not to limit the present invention. Therefore, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present invention shall fall within the protection scope of the present invention. Furthermore, it is intended that the appended claims of the present invention embrace all changes and modifications that come within the scope and metesques of the appended claims, or equivalents of such scope and metes and bounds.

Claims (6)

1. A method for accurately characterization of the Beidou space-time reference based on state domain space, characterized in that, comprising the steps: Step 1, obtain the position of the satellite through the SSR satellite orbit correction information; Step 2, correcting the SSR satellite clock to obtain the satellite clock; Step 3, through SSR satellite bias correction, obtain pseudorange and phase observations that do not contain individual time-dependent bias; Step 4, obtain the oblique total electron content information through the SSR vertical total electron content information, and then obtain the pseudorange and phase observations that do not include ionospheric bias; In step 5, the user ranging accuracy is obtained through the SSR user ranging accuracy index. 2. The Beidou space-time reference accurate characterization method based on state domain space according to claim 1, wherein in step 1, the SSR satellite orbit correction information uses a satellite fixed coordinate system, which includes radial, tangential and normal directions Orbit correction parameters in three directions. 3. the BeiDou space-time reference accurate characterization method based on state domain space according to claim 1, is characterized in that, in step 2, SSR satellite orbit correction is to the correction of the satellite orbit according to the satellite broadcast parameter calculation of GNSS-ICD algorithm , SSR satellite clock corrections are also calculated with corresponding calculations based on specific GNSS satellite broadcast parameters based on the GNSS-ICD algorithm. 4. The Beidou space-time reference accurate characterization method based on state domain space according to claim 1, characterized in that, in step 3, the pseudorange of the individual time-dependent deviation is not included and phase /> Observations are obtained from pseudorange and phase raw observations through the following mathematical expression: , , in, and /> SSR bias correction corresponding to pseudorange and phase respectively, /> and /> are pseudorange and phase raw observations, respectively. 5. The Beidou space-time reference accurate characterization method based on the state domain space according to claim 1, wherein in step 5, the SSR user ranging accuracy index is obtained through the SSR URA message of each satellite, and the index and numerical value are obtained. The corresponding relationship is converted into user ranging accuracy. 6. A Beidou space-time reference accurate characterization system based on state domain space, characterized in that it includes: The satellite position acquisition module is used to correct the information through the SSR satellite orbit to obtain the position of the satellite; The satellite clock acquisition module is used for correcting the SSR satellite clock to obtain the satellite clock; The pseudorange and phase observation module is used to obtain pseudorange and phase observations that do not contain individual time-dependent biases through SSR satellite bias correction; The pseudorange and phase observation module without ionospheric bias is used to obtain the tilted total electron content (STEC) information through the SSR vertical total electron content (VTEC) information, and then obtain the pseudorange and phase observation without ionospheric bias; The user ranging accuracy module is configured to use the SSR user ranging accuracy (URA) index to obtain the user ranging accuracy through a table.